U.S. patent application number 11/762651 was filed with the patent office on 2008-12-18 for apparatus and method for immersion lithography.
This patent application is currently assigned to TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.. Invention is credited to Ching-Yu Chang, Tsai-Sheng Gau, Burn Jeng Lin.
Application Number | 20080309891 11/762651 |
Document ID | / |
Family ID | 40131975 |
Filed Date | 2008-12-18 |
United States Patent
Application |
20080309891 |
Kind Code |
A1 |
Chang; Ching-Yu ; et
al. |
December 18, 2008 |
APPARATUS AND METHOD FOR IMMERSION LITHOGRAPHY
Abstract
Immersion lithography apparatus and method using a shield module
are provided. An immersion lithography apparatus including a lens
module having an imaging lens, a substrate table positioned beneath
the lens module and configured for holding a substrate for
processing, a fluid module for providing an immersion fluid to a
space between the lens module and the substrate on the substrate
table, and a shield module for covering an edge of the substrate
during processing.
Inventors: |
Chang; Ching-Yu; (Yilang
County, TW) ; Gau; Tsai-Sheng; (Hsinchu, TW) ;
Lin; Burn Jeng; (Hsin-Chu, TW) |
Correspondence
Address: |
HAYNES AND BOONE, LLP
901 Main Street, Suite 3100
Dallas
TX
75202
US
|
Assignee: |
TAIWAN SEMICONDUCTOR MANUFACTURING
COMPANY, LTD.
Hsin-Chu
TW
|
Family ID: |
40131975 |
Appl. No.: |
11/762651 |
Filed: |
June 13, 2007 |
Current U.S.
Class: |
355/30 |
Current CPC
Class: |
G03F 7/70341
20130101 |
Class at
Publication: |
355/30 |
International
Class: |
G03B 27/52 20060101
G03B027/52 |
Claims
1. An immersion lithography apparatus, comprising: a lens module
including an imaging lens; a substrate table positioned beneath the
lens module and configured for holding a substrate for processing;
a fluid module for providing an immersion fluid to a space between
the lens module and the substrate on the substrate table; and a
shield module for covering an edge of the substrate during
processing.
2. The apparatus of claim 1, wherein the shield module includes no
openings.
3. The apparatus of claim 1, wherein the shield module includes at
least one opening.
4. The apparatus of claim 3, wherein the at least one opening
includes a slit.
5. The apparatus of claim 1, wherein the shield module includes at
least two separate sections that are adjustable to cover an area
around the edge of the substrate during processing.
6. The apparatus of claim 6, wherein the at least two separate
sections are configured to move radially.
7. The apparatus of claim 1, wherein the substrate table includes a
plurality of drain lines disposed proximate to the edge of the
substrate and underneath the shield module, wherein the plurality
of drain lines are configured to remove a portion of the immersion
fluid provided to the space between the lens module and the
substrate on the substrate table.
8. The apparatus of claim 7, wherein the shield module includes at
least one fluid line for supplying a fluid to a space between the
edge of the substrate and the shield module when the immersion
fluid does not cover the edge of the substrate during
processing.
9. The apparatus of claim 7, wherein the substrate table includes
at least one fluid line for supplying a fluid to a space between
the edge of the substrate and the shield module when the immersion
fluid does not cover the edge of the substrate during
processing.
10. An immersion lithography method, comprising: loading and
securing a wafer onto a wafer stage disposed beneath an imaging
lens; covering an edge of the wafer with a shield module; moving
the wafer stage so that an area of the wafer to be exposed is
aligned with the imaging lens; performing an exposure process to
the area of the wafer; and moving the wafer stage to a next
location and repeating some of the previous steps until exposure of
the entire wafer is complete.
11. The method of claim 10, wherein the step of loading and
securing the wafer onto a wafer stage includes moving at least two
separate sections of the shield module radially outward.
12. The method of claim 10, wherein the step of covering the edge
of the wafer includes moving at least two separate sections of the
shield module radially inward to cover an area around the edge of
the wafer.
13. The method of claim 10, further comprising the step of
adjusting the shield module according to a recipe setting.
14. The method of claim 10, further comprising the step of
supplying a fluid to a space between the edge of the wafer and the
shield module when the immersion fluid does not cover the edge of
the wafer during processing.
15. The method of claim 10, further comprising the steps of:
providing a wafer having a photoresist layer formed thereon;
performing a post-exposure bake on the exposed photoresist layer;
and developing the exposed photoresist layer to form a patterned
photoresist layer.
16. An immersion lithography system, comprising: an immersion hood
including an imaging lens module and a fluid retaining module,
wherein the fluid retaining module provides an immersion fluid, a
wafer stage disposed beneath the immersion hood for securing a
wafer to be processed; a drain system for removing the immersion
fluid provided to a space between the immersion hood and the wafer
on the wafer stage, wherein the drain system includes a plurality
of extraction lines located in the immersion hood and wafer stage;
and a cover plate for covering an area around an edge of the wafer
during processing.
17. The system of claim 16, wherein the cover plate includes a
plurality of sections, wherein each of the plurality of sections is
configured to move radially such that the covered area around the
edge of the wafer can be adjusted.
18. The system of claim 16, wherein the cover plate includes at
least one fluid line for supplying a fluid to the edge of the
wafer.
19. The system of claim 16, wherein the wafer stage includes at
least one fluid line for supplying a fluid to the edge of the
wafer.
20. The system of claim 16, wherein the immersion hood includes a
purge unit for purging a space between the edge of the wafer and
the cover plate with a fluid.
Description
BACKGROUND
[0001] The present disclosure relates generally to immersion
photolithography and, more particularly, to an apparatus and method
for shielding an edge of a wafer during an immersion
photolithography process.
[0002] Immersion lithography is a relatively new advancement in
photolithography, in which the exposure procedure is performed with
a fluid filling the space between the surface of the wafer and the
lens. Using immersion lithography, higher numerical apertures can
be built than when using lenses in air, resulting in improved
resolution. Further, immersion lithography provides enhanced
depth-of-focus (DOF) for printing ever smaller features. A
photoresist or resist layer is formed on the surface of the wafer
for patterning. The resist layer is applied to the surface of the
wafer by a spin coating process. However, there may be resist that
forms on an edge of the wafer during spin coating and, when dry,
can flake off and cause particles to contaminate active areas of
the wafer and/or processing equipment such as the immersion
lithography system. The process wafer can also easily accumulate
particles at the wafer edge area, when a solvent removes the edge
resist, such particles are uncovered and may contaminate the
immersion lithography system. This can lead to pattern defects,
pattern distortion, and/or pattern loss.
[0003] Therefore, what is needed is a simple and cost-effective
apparatus and method for shielding the edge of the wafer to
minimize contaminations being introduced to the immersion
lithography system.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The present disclosure is best understood from the following
detailed description when read with the accompanying figures. It is
emphasized that, in accordance with the standard practice in the
industry, various features are not drawn to scale. In fact, the
dimensions of the various features may be arbitrarily increased or
reduced for clarity of discussion.
[0005] FIG. 1 is a schematic view of a lens-based ("LBC") immersion
system.
[0006] FIG. 2 is a schematic view of a wafer-based ("WBC")
immersion system.
[0007] FIGS. 3A and 3B are enhanced schematic views of a problem
associated with the LBC immersion system of FIG. 1 and WBC
immersion system of FIG. 2, respectively.
[0008] FIGS. 4A and 4B are a cross-sectional view and top view,
respectively, of a shield structure that may be implemented with
the LBC and WBC immersion system of FIGS. 1 and 2.
[0009] FIGS. 5A through 5C are top views of several shield modules
that may be utilized in the immersion systems of FIGS. 1 and 2.
[0010] FIG. 6 is an enhanced schematic view of part of an immersion
lithography system utilizing one of the shield modules of FIGS. 5A
through 5C.
[0011] FIG. 7 is an enhanced schematic view of part of the
immersion lithography system of FIG. 6 with the shield module in a
closed position.
[0012] FIG. 8 is a schematic view of part of an immersion
lithography system having a plurality of fluid or air lines.
[0013] FIG. 9 is a schematic view of part of an immersion
lithography system having a purging unit.
[0014] FIG. 10 is a flowchart of an immersion lithography method
that may be implemented in the immersion lithography system of
FIGS. 6-9.
DETAILED DESCRIPTION
[0015] The present disclosure relates generally to the liquid
immersion photolithography systems, and, more particularly, to an
immersion photolithography system using a sealed wafer bath. It is
understood, however, that specific embodiments are provided as
examples to teach the broader inventive concept, and one of
ordinary skill in the art can easily apply the teachings of the
present disclosure to other methods and systems. Also, it is
understood that the methods and systems discussed in the present
disclosure include some conventional structures and/or steps. Since
these structures and steps are well known in the art, they will
only be discussed in a general level of detail. Furthermore,
reference numbers are repeated throughout the drawings for the sake
of convenience and example, and such repetition does not indicate
any required combination of features or steps throughout the
drawings.
[0016] Generally, there are two system configurations in immersion
lithography, including a lens-based ("LBC") system and a
wafer-based ("WBC") system. With LBC systems, immersion fluid is
selectively provided to and extracted from a small region between a
lens system and a wafer and the immersion assembly is stationary
with respect to the lens system as the wafer is stepped or
scanned.
[0017] Referring to FIG. 1, illustrated is a schematic view of a
LBC system 100. The system 100 may include a wafer table 110 for
holding a wafer 112 to be processed by the system 100. The wafer
table 110 can be a wafer stage or include a wafer stage as a part
thereof. The wafer table 110 is operable to secure and move the
wafer 112 relative to the system 100. For example, the wafer table
110 may secure the wafer 112 via a vacuum chuck 114. The wafer
table 110 may also be capable of translational and/or rotational
displacement for wafer alignment, stepping, and scanning. The wafer
table 110 may include various components suitable to perform
precise movement.
[0018] The wafer 112 to be held by the wafer table 110 and
processed by the system 100 may be a semiconductor wafer (or
substrate) such as a silicon wafer. Alternatively, the
semiconductor wafer may include an elementary semiconductor, a
compound semiconductor, an alloy semiconductor, or combinations
thereof. The semiconductor wafer may include one or more material
layers such as poly-silicon, metal, and/or dielectric, to be
patterned. The wafer 112 may further include an imaging layer 116
formed thereon. The imaging layer 116 can be a photoresist layer
(resist layer, photosensitive layer, patterning layer) that is
responsive to an exposure process for creating patterns. The
imaging layer 116 may be a positive or negative type resist
material and may have a multi-layer structure. One exemplary resist
material is chemical amplifier (CA) resist.
[0019] The LBC system 100 may further include one or more imaging
lens assemblies or systems (referred to as a "lens system") 120.
The semiconductor wafer may be positioned on a wafer table 110
under the lens system 120. The lens system 120 may further include
or be integral to an illumination system (e.g., a condenser) which
may have a single lens or multiple lenses and/or other lens
components. For example, the illumination system may include
microlens arrays, shadow masks, and/or other structures. The lens
system 120 may further include an objective lens which may have a
single lens element or a plurality of lens elements. Each lens
element may include a transparent substrate and may further include
a plurality of coating layers. The transparent substrate may be a
conventional objective lens, and may be made of fused silica
(SiO2), calcium-fluoride (CaF2), lithium fluoride (LiF), barium
fluoride (BaF2), or other suitable material. The materials used for
each lens element may be chosen based on the wavelength of light
used in the lithography process to minimize absorption and
scattering.
[0020] The system 100 may also include an immersion fluid retaining
module 130 for holding a fluid 132 such as an immersion fluid. The
immersion fluid retaining module 130 may be positioned proximate
(such as around) the lens system 120 and designed for other
functions, in addition to holding the immersion fluid. The
immersion fluid retaining module 130 and the lens system 120 may
make up (at least in part) an immersion hood 134. The immersion
fluid may include water (water solution or de-ionized water (DIW)),
high n fluid (n is index of refraction, the n value at 193 nm
wavelength here is larger than 1.44), gas, or other suitable
fluid.
[0021] The immersion fluid retaining module 130 may include various
apertures (or nozzles) for providing the immersion fluid for an
exposure process. Particularly, the module 130 may include an
aperture 136 as an immersion fluid inlet to provide and transfer
the immersion fluid into a space 140 between the lens system 120
and the wafer 112 on the wafer table 110. The immersion fluid
substantially covers an area of the wafer 112 that will be exposed
to form a pattern thereon. The module 130 may also include an
aperture 138 as an immersion fluid outlet to remove and transfer
the immersion fluid from the space 140. It is understood that the
immersion fluid may be provided to and from the space 140 at a
sufficient rate by components suitable for this type of movement.
Additionally, the immersion fluid outlet may be part of a drain
system for removing the immersion fluid from the LBC system
100.
[0022] The drain system may further include a plurality of
extraction (or suck back) lines 150, 152 located proximate to an
edge of the wafer 112 for removing a portion of the immersion fluid
provided to the space 140 between the lens system 120 and the wafer
112 on the wafer table 110. Alternatively, the plurality of
extraction lines 150, 152 may be part of a stage drain system. The
extraction lines 150, 152 may merge into a single line 154 that
provides a such back force 156 to remove the immersion fluid from
the system 100. The extraction lines 150, 152 may be incorporated
or integrated with the wafer table 110. It is understood that the
number of extraction lines may vary and will depend on the type of
immersion lithography system that is used.
[0023] The LBC system 100 may further include a radiation source
(not shown). The radiation source may be a suitable ultraviolet
(UV) or extreme ultraviolet (EUV) light source. For example, the
radiation source may be a mercury lamp having a wavelength of 436
nm (G-line) or 365 nm (I-line); a Krypton Fluoride (KrF) excimer
laser with wavelength of 248 nm; an Argon Fluoride (ArF) excimer
laser with a wavelength of 193 nm; a Fluoride (F2) excimer laser
with a wavelength of 157 nm; or other light sources having a
desired wavelength (e.g., below approximately 100 nm).
[0024] A photomask (also referred to as a mask or a reticle) may be
introduced into the system 100 during an immersion lithography
process. The mask may include a transparent substrate and a
patterned absorption layer. The transparent substrate may use fused
silica (SiO2) relatively free of defects, such as borosilicate
glass and soda-lime glass. The transparent substrate may use
calcium fluoride and/or other suitable materials. The patterned
absorption layer may be formed using a plurality of processes and a
plurality of materials, such as depositing a metal film made with
chromium (Cr) and iron oxide, or an inorganic film made with MoSi,
ZrSiO, SiN, and/or TiN.
[0025] In contrast to LBC systems, in WBC systems, a wafer may be
completely immersed in immersion fluid in a circulating tank in a
wafer table. Referring to FIG. 2, illustrated is a schematic view
of a WBC system 200. Similar features in FIGS. 1 and 2 are numbered
the same for simplicity and clarity. In the WBC system, an
immersion fluid is selectively introduced into and removed from a
region 202 between a lens system 120 and a wafer 112 via a fluid
inlet 204 and a fluid outlet 206. The WBC system may include a
wafer gate 208 disposed on either side of the wafer table 110 for
retaining the immersion fluid in the region 202. Additionally, the
immersion fluid may be removed from the region 202 by a plurality
of extraction (or suck back) lines 150, 152 located proximate to an
edge of the wafer 112 and a drain line 208 located at the wafer
gate 208. It is understood that other drain lines may be provided
to aid in removing the immersion fluid. The immersion fluid may
circulate in the region 202 under and over the wafer table 110
continuously and may be filtered and temperature-regulated as it
moves across the surface area of the wafer 112. The immersion fluid
can be completely drained from the region 202 to allow for loading
and unloading of the wafer 112. The system 200 may include a cover
210 that prevents the immersion fluid in the region 202 from
spilling over and foreign particles from being introduced to the
immersion fluid.
[0026] Referring now to FIGS. 3A and 3B, illustrated are enhanced
schematic views of one of the problems associated with the systems
described in FIGS. 1 and 2 above. Similar features in FIGS. 1 and
3A, and in FIGS. 2 and 3B are numbered the same for simplicity and
clarity. In FIGS. 3A and 3B, a photoresist layer 116 may be formed
on a surface of the wafer 112 for patterning. The photoresist at
the edge 300 of the wafer 112 (also referred to as the edge bead)
may be thicker than the rest of the photoresist layer 116 or may be
etched away by a solvent to clear the edge area of the photoresist
covering. This leaves the possibility of broken resist fragments
and/or particles from the edge area 302 under the movement of the
immersion fluid that may contaminate the systems 100, 200.
[0027] Referring now to FIGS. 4A and 4B, illustrated are a
cross-sectional view and top view of a shield section 400 that may
be implemented with the LBC and WBC immersion system 100, 200 of
FIGS. 1 and 2. The shield section 400 may include a body portion
402 and a cover portion 404. The body portion 402 may be coupled to
the immersion system such that the shield section 400 may be moved
in various positions as will be discussed later. The cover portion
404 may be curved so that it can shield an area around an edge of
the wafer. The shield section 400 may be made of stainless steel or
alloy. Alternatively, the shield section 400 may optionally be made
of quartz or other suitable transparent material. In FIG. 4B, the
shield section 400 may include a plurality of openings for
hydrodynamic control of the immersion fluid. In one embodiment, the
shield section 400 may include a plurality of holes or circles 406.
In another embodiment, the shield section 400 may include a
plurality of slits 408. It is understood that the openings may
include various shapes such as a polygon, oval, irregular shape, or
combinations thereof. Alternative, the shield section 400 may be
free of openings 410.
[0028] Referring now to FIGS. 5A through 5C, illustrated are top
views of several shield modules utilizing a plurality of shield
sections 400 of FIG. 4A. In FIG. 5A, a shield module 510 may
include two shield sections 511, 512. In an open position, the two
shield sections 511, 512 may be moved radially outward (e.g., away
from the center of the wafer) such that a wafer may be loaded in a
space defined by the two shield sections. An edge 514 of the wafer
is proximate to the cover portion 404 (FIG. 4A) of the shield
sections 511, 512. In a close position, the two shield sections
511, 512 may be moved 516, 518 radially inward (e.g., towards the
center of the wafer) such that the cover portion 404 of the shield
sections 511, 512 covers 520 an area around the edge of the wafer.
In FIG. 5B, a shield module 520 is similar to the shield
configuration 510 of FIG. 5A except that it includes three shield
sections 521, 522, 523 for covering the area around the edge of the
wafer. In FIG. 5C, a shield module 530 is similar to the shield
configuration 510 of FIG. 5A except that it includes four shield
sections 531, 532, 533, 534 for covering the area around the edge
of the wafer. The shield sections may be moved radially
inward/outward by a mechanical, electromechanical, pneumatic, or
other suitable mechanism. Additionally, it is understood that the
shield modules described above mere examples and that the number of
shield sections implemented may vary and will depend on the design
specification of the immersion lithography system. Alternatively,
the shield module may include a single cover plate or section.
[0029] Referring now to FIG. 6, illustrated is an enhanced
schematic view of part of an immersion lithography system 600
utilizing one of the shield modules 510, 520, 530 of FIGS. 5A
through 5C. The immersion lithography system is similar to the LBC
system of FIG. 1 except for the additional features described
below. Similar features in FIGS. 1 and 6 are numbered the same for
clarity. It is understood that only one shield section of the
shield module is shown for simplicity. As previously discussed, the
shield section 400 may include a body portion 402 and a cover
portion 404. The body portion 402 may be secured in a space 602
around a wafer stage 110. The body portion 402 may be moved within
the space 602 such that an area around the wafer edge 604 that is
shielded by the cover portion 404 can be adjusted. The shield
section 400 may be moved in an open position as was described in
FIG. 5A. Accordingly, a wafer 112 having a photoresist layer 116
formed thereon may be loaded and secured on the wafer stage 110. In
the open position, the cover portion 404 does not shield the wafer
edge 604.
[0030] The system 600 may further include a plurality of inlets and
outlets for performing various functions. For example, a first line
606 may provide a fluid such as de-ionized water to clean a stage
drain extraction line 152. The first line 606 may also provide the
fluid to control a wafer surface moisture since there are instances
when the immersion fluid does not cover the wafer edge 604.
Alternatively, the first line 606 may be used as a back up drain
line for the system. The second and third lines 608, 610 may be
configured as an inlet or outlet. The second line 608 may provide a
fluid for cleaning the cover portion 404 and the third line 610 may
remove the fluid after the cleaning. Alternatively, the second line
608 may provide a fluid for maintaining temperature stability
around the area 602 and the third line 610 may remove the
fluid.
[0031] Referring now to FIG. 7, illustrated is an enhanced
schematic view of part of the immersion lithography system 600 of
FIG. 6 with the shield section 400 in a closed position. As
previously discussed, the shield section 400 may be moved 700
radially inward such that the cover portion 404 may shield the area
around the edge 604 of the wafer 112. For example, the area that is
3 mm from the edge 604 of the wafer 112 may be covered. A thickness
of the cover portion 404 may range between 10 to 100 .mu.m. It is
understood that the dimensions disclosed herein are mere examples
and that other dimensions may be implemented depending on the
specific application.
[0032] The wafer stage 110 may be positioned beneath the immersion
hood and an immersion fluid is provided to a space between the lens
system and the wafer. The immersion fluid may be removed via a
fluid outlet 138 of the immersion hood 134 and the extraction line
152 of the wafer table 110. Accordingly, the particles and/or
fragments at the wafer edge 604 will be trapped by the cover
portion 404 and will be removed by a suck back force 156 of an
extraction line 152 located proximate to the wafer edge 604. The
particles and/or fragments are prevented from circulating back into
the immersion fluid and/or photoresist layer and thus,
contaminating the system. The particles and/or fragments at the
wafer edge 604 will also be trapped and removed when the wafer
table 110 may be moved to a next exposure location. Additionally,
the shield section 400 may be moved 700 such that the area around
the wafer edge 604 that is shielded by the cover portion 404 can be
adjusted. This can be done according to a particular recipe. It is
understood that the shield module described in FIGS. 6 and 7 may
also be implemented with the WBC system 200 of FIG. 2 in a similar
manner.
[0033] Referring now to FIG. 8, illustrated is a schematic view of
part of an immersion lithography system 800 having a plurality of
fluid or air lines. The immersion lithography system 800 is similar
to the immersion lithography system 600 of FIG. 6 except for the
following additional features discussed below. Similar features in
FIGS. 6 and 8 are numbered the same for simplicity and clarity. The
immersion lithography system 800 may include a plurality of fluid
or air lines disposed at various locations. When the immersion
fluid does not cover a wafer edge, a stage drain extraction line
152 continues to provide a suck back force 156 that sucks air from
the wafer surface. As a result, an evaporation phenomena may be
enhanced at the wafer edge 604 and thus, may decrease a surface
temperature at the wafer edge. This temperature difference may
adversely affect the exposure process. A first fluid line 802 may
be located under a wafer table 110, a second fluid line 804 may be
located under the shield section 400, and a third fluid line 806
may be located inside the shield section 400. The first, second,
and third fluid lines 802, 804, 806 may provide air, liquid, or
moist air for suck back stability control of the extraction line
152. This may reduce the cooling effect of the wafer edge and
surface.
[0034] Referring now to FIG. 9, illustrated is a cross-sectional
view of part of an immersion lithography system 900 having a
purging unit. The immersion lithography system 900 is similar to
the immersion lithography system 600 of FIG. 6 except for the
following additional features discussed below. Similar features in
FIGS. 6 and 9 are numbered the same for simplicity and clarity. The
immersion lithography system 900 may include a purging unit 902
positioned with an immersion hood 134. During processing, the wafer
table 110 may moved 904 from the center of the immersion hood 134
to the edge of the immersion hood to pattern the center of the
wafer 112. Accordingly, the immersion fluid no longer covers the
wafer edge 604. However, a tailing effect 906 of the immersion
fluid and step height of the photoresist layer 116, as the wafer
table 110 is moved, may generate water drop residues 908 at a slit
area of the wafer edge 604 that was covered by the shield section
400. The purging unit 902 may be configured to purge 910 gas, air,
or other suitable fluid to dry and/or clean the slit area of the
wafer edge 604.
[0035] Referring now to FIG. 10, illustrated is a flowchart of an
immersion lithography method 1000 according to one or more
embodiments of the present disclosure. The method 1000 may be
implemented in the immersion lithography system of FIGS. 6 through
9. The method 1000 begins with step 1010 in which a wafer may be
loaded and secured on a wafer stage via a vacuum chuck. The wafer
stage may be disposed beneath an immersion hood. The wafer may
include a photoresist layer ready for patterning. The method 1000
continues with step 1020 in which an edge of the wafer may be
covered by a shield module similar to the one described in FIGS. 5A
through 5C. The particles and/or fragments at the wafer edge will
be trapped by the shield module and removed by a stage drain
extraction line located proximate to the wafer edge.
[0036] The method 1000 continues with step 1030 in which the wafer
stage may be moved a location so that an area of the photoresist
layer to be exposed may be aligned with the lens system of the
immersion hood in which immersion fluid is filled between the lens
and wafer. The method 1000 continues with step 1040 in which an
immersion fluid may be continuously provided to a space between the
lens system and the wafer. It is understood that the immersion
fluid may be provided and removed at a substantially constant rate.
The immersion fluid may be removed from the space by the drain
system including extraction lines located with the immersion hood
and wafer stage. If the immersion fluid does not cover an edge of
the wafer, the extraction lines located proximate to the edge may
be provided with a fluid such as moist air for minimizing a cooling
effect on the surface of the wafer.
[0037] The method 1000 continues with step 1050 in which an
exposure process may be performed on the area of the photoresist
layer to form a pattern. The exposure process may include exposing
the area with a radiation source through a photomask to transfer a
pattern to the photoresist. The method 1000 continues with step
1060 in which a decision may be made as to whether exposure of the
entire wafer has been completed.
[0038] If the answer is no, the method 1000 repeats steps 1030
through 1060. If the answer is yes, the method 1000 continues with
step 1070 in which the shield module opens and the wafer may be
unloaded from the immersion lithography system. The exposed
photoresist layer may go through further processing steps such as a
post-exposure bake process and a development process to form a
patterned photoresist layer. These processes are known in the art
and thus, are not described in detail here.
[0039] Although only a few exemplary embodiments of this invention
have been described in detail above, those skilled in the art will
readily appreciate that many modifications are possible in the
exemplary embodiments without materially departing from the novel
teachings and advantages of this invention. It is understood that
various different combinations of the above-listed embodiments and
steps can be used in various sequences or in parallel, and there is
no particular step that is critical or required. Furthermore,
features illustrated and discussed above with respect to some
embodiments can be combined with features illustrated and discussed
above with respect to other embodiments. Accordingly, all such
modifications are intended to be included within the scope of this
invention.
[0040] Thus, provided is an immersion lithography apparatus
including a lens module having an imaging lens, a substrate table
positioned beneath the lens module and configured for holding a
substrate for processing, a fluid module for providing an immersion
fluid to a space between the lens module and the substrate on the
substrate table, and a shield module for covering an edge of the
substrate during processing. In some embodiments, the shield module
includes no openings. In some other embodiments, the shield module
includes at least one opening. In other embodiments, the at least
one opening includes a slit. In still other embodiments, the shield
module includes at least two separate sections that are adjustable
to cover an area around the edge of the substrate during
processing. In some embodiments, the at least two separate sections
are configured to move radially.
[0041] In other embodiments, the substrate table includes a
plurality of drain lines disposed proximate to the edge of the
substrate and underneath the shield module. The plurality of drain
lines are configured to remove a portion of the immersion fluid
provided to the space between the lens module and the substrate on
the substrate table. In some other embodiments, the shield module
includes at least one fluid line for supplying a fluid to a space
between the edge of the substrate and the shield module when the
immersion fluid does not cover the edge of the substrate. In still
other embodiments, the substrate table includes at least one fluid
line for supplying a fluid to a space between the edge of the
substrate and the shield module when the immersion fluid does not
cover the edge of the substrate.
[0042] Also provided is an immersion lithography method including
the steps of loading and securing a wafer onto a wafer stage
disposed beneath an imaging lens; covering an edge of the wafer
stage by a shield module; moving the wafer stage so that an area of
the wafer to be exposed is aligned with the imaging lens;
performing an exposure process to the area of the wafer; and moving
the wafer stage to a next location and repeating some of the
previous steps until exposure of the entire wafer is complete. In
some embodiments, the step of loading and securing the wafer
includes moving at least two separate sections of the shield module
radially outward. In some other embodiments, the step of covering
the edge of the wafer includes moving at least two separate
sections of the shield module radially inward to cover an area
around the edge of the wafer.
[0043] In other embodiments, the method further includes the step
of adjusting the shield module according to a recipe setting. In
some other embodiments, the method further includes the step of
supplying a fluid to a space between the edge of the wafer and the
shield module when the immersion fluid does not cover the edge of
the wafer during processing. In still other embodiments, the method
further includes the steps of providing a wafer having a
photoresist layer formed thereon; performing a post-exposure bake
on the exposed photoresist layer; and developing the exposed
photoresist layer to form a patterned photoresist layer.
[0044] Additionally, an immersion lithography system is provided
which includes an immersion hood having an imaging lens module and
a fluid retaining module, the fluid retaining module provides an
immersion fluid; a wafer stage disposed beneath the immersion hood
for securing a wafer to be processed; a drain system for removing
the immersion fluid provided to a space between the immersion hood
and the wafer on the wafer stage, the drain system includes a
plurality of extraction lines located in the immersion hood and the
wafer stage; and a cover plate for covering an area around an edge
of the wafer during processing. In some embodiments, the cover
plate includes a plurality of sections, each section is configured
to move radially such that the covered area around the edge of the
wafer can be adjusted. In some other embodiments, the cover plate
includes at least one fluid line for supplying a fluid to the edge
of the wafer. In other embodiments, the wafer stage includes at
least one fluid line for supplying a fluid to the edge of the
wafer. In still other embodiments, the immersion hood include at
least one purge unit for purging a space between the edge of the
wafer and the cover plate with a fluid.
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